Unless I’m missing something, you can do this fairly simply already. I have a post-install script I run on all of my machines which sets up all network shares and runs ‘apt install whole bunch of packages’ to get things into a ready-to-roll state.

If they do no push back, then they are just kicking the can down the road, at great expense to themselves. This is exactly the sort of pushback needed to get bambu to walk back their push towards a walled garden.